Field of the Invention
The invention relates to a plant for processing wafers in which wafers are transported between fabrication units and measuring units.
Plants of this type include a large number of fabrication units that can be used to carry out different fabrication processes. These fabrication processes are, in particular, etching processes, wet chemical processes, diffusion processes, and diverse cleaning processes such as the CMP (Chemical Mechanical Polishing) process. For each of these processes, one or more fabrication units is or are provided, in which various fabrication steps of a fabrication process are carried out.
In addition, such plants include a large number of measuring units. In the measuring units, the processing quality of one or more fabrication steps of a fabrication process is checked.
The entire fabrication process is subject to strict cleanliness requirements, and therefore, the fabrication units and the measuring units are arranged in a clean room or in a system of clean rooms.
The wafers are placed in containers designed as cassettes and are fed to the individual fabrication units in predetermined batch sizes using a transport system. In addition, the outward transport of the cassettes after the processing of these wafers is carried out using the transport system.
The transport system typically has a conveyor system having a number of conveyors which, for example, are designed in the form of roller conveyors. In this case, the cassettes with the wafers are transported resting on the roller conveyors. Alternatively, the conveyor system may also include continuous conveyors, suspension conveyors or the like.
In order to control plants of this type, a material disposition system is normally provided. By using this material disposition system, wafers in specific numbers are removed from a storage device or similar apparatus and are combined into batches. For the individual batches, working plans are formulated which contain the individual processing steps that are carried out with the wafers in the individual fabrication units and measuring units as they pass through the plant. In addition, the allocation of priorities for the individual wafers is carried out using the material disposition system. By using this established priority, the result is a specific processing sequence for the wafers of the different batches.
Finally, the wafers are fed by the material disposition system to the transport system, and the transport system feeds the containers with the wafers to the individual fabrication units and measuring units. Here, the containers in the transport system are loaded with predefined batch-related transport jobs. The transport jobs contain, in particular, the destinations for the individual containers. The destinations are the fabrication units and the measuring units.
On the basis of these transport jobs, the containers are fed to the individual destinations. Only in the event that a fabrication or measuring unit is out of operation will a fault message be output to the material disposition system, so that the further delivery of wafers is suppressed. However, the disadvantage here is that the transport jobs can still be given to individual fabrication and measuring units when, although the latter are still serviceable, they are already overloaded. In this case, the wafers back up in front of the relevant fabrication and measuring units. As a result of the waiting times which occur during the processing of the wafers in this case, their passage time through the plant is increased undesirably, as a result of which, in particular, the production costs for the wafers are also increased.
It is accordingly an object of the invention to provide a plant of the type mentioned at the beginning which overcomes the above-mentioned disadvantages of the prior art apparatus of this general type.
In particular, it is an object of the invention to provide a plant of the type mentioned at the beginning such that the passage times of the wafers during their processing in the plant are as low as possible.
With the foregoing and other objects in view there is provided, in accordance with the invention, a plant for processing wafers that includes a plurality of units. Each one of the plurality of the units includes either a fabrication unit or a measuring unit. The plant also includes a transport system for transporting the wafers. Each respective one of the plurality of the units includes a loading and unloading station having at least one loading port for feeding in the wafers, a processing flap for closing the loading port, at least one unloading port for discharging the wafers, and a processing flap for closing the unloading port. Each respective one of the plurality of the units includes a registration system configured for registering a feeding-in and a discharging of the wafers to and from the respective one of the plurality of the units in order to determine a wafer occupancy in the respective one of the plurality of the units. For each respective one of the plurality of the units, a selected request is generated as a function of the wafer occupancy in the respective one of the plurality of the units. The selected request is either a supply request for the respective one of the plurality of the units or a disposal request for the respective one of the plurality of the units. The registration system of each respective one of the plurality of the units has a sensor configuration for registering the number of the wafers that are fed-in to the respective one of the plurality of the units and that are discharged from the respective one of the plurality of the units. The sensor configuration of the registration system of each respective one of the plurality of the units enables the registration of an actuation of the processing flap for closing the loading port of the respective one of the plurality of the units. The sensor configuration of the registration system of each respective one of the plurality of the units also enables the registration of an actuation of the processing flap for closing the unloading port of the respective one of the plurality of the units.
According to the invention, the fabrication units and measuring units of the plant are each assigned a registration system, with which the feed and discharge of the wafers to and from the respective fabrication or measuring unit can be registered in order to determine their wafer occupancy. Depending on this occupancy, a supply or disposal request for the respective fabrication or measuring unit can be generated.
The registration system can therefore include, in particular, a sensor configuration that is used to count the wafers that are fed to a fabrication unit or measuring unit or discharged from the latter. At the same time, the individual wafers or the containers in which the wafers are transported can particularly advantageously be identified. Depending on the information registered in the registration system, supply and disposal requests for the individual fabrication and measuring units are preferably generated in a control station that is coupled to the individual fabrication and measuring units. Using the capacity utilizations of the individual fabrication and measuring units, known in the control station, the units are fed with wafers in suitable numbers via a suitable selection of transport jobs. Since the wafers can preferably be identified in the registration systems, the feed of the individual wafers in the fabrication units and measuring units is also carried out in an optimized manner with regard to the current processing states and in accordance with the processing steps that can be carried out in the fabrication and measuring units.
As a result, waiting times of the wafers in front of the individual fabrication and measuring units can largely be avoided, and the processing capacities of the fabrication and measuring units can be used optimally.
It is particularly advantageous that the registration systems can be designed as modules that can be retrofitted to existing fabrication and measuring units.
With the known fabrication and measuring units in use, the processing capacities available there cannot be registered. In addition, there are no interfaces via which such information could be output. In order to make such information available, it would be necessary for the fabrication and measuring unit to be reconceived in significant areas, which would lead to comprehensive design changes. This would not only give rise to considerable investment costs but would also be extremely time-consuming.
However, with the registration systems designed as modules, the functional scope of the fabrication and measuring units can be expanded quickly and without great financial expenditure.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a plant for processing wafers, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.